Question

(a) Complete the following statement.
An object is in equilibrium when both the .................................................................. and the
.................................................................. on the object are zero.

(b) Fig. 3.1 shows a ladder AB. End A of the ladder rests against a vertical wall. End B rests on rough ground.

Fig. 3.1 shows two of the forces acting on the ladder. The only force on the ladder at A is F, which acts at right-angles to the wall. The weight of the ladder is 240 N acting at the centre of mass of the ladder.
(i) 1. Calculate the moment of the weight of the ladder about point B.
2. Write an expression, in terms of F, for the moment of F about point B.

(ii) Use your answers from (i) to calculate F.

(iii) Explain why there must be an upwards force acting on the ladder at B.

Answer 1

a) net force and the net torque

Explanation:

Generally body tends to be in equilibrium if it is in translational as well as rotational equilibrium.

For translational equilibrium of a body the total force or the net force acting on it should be negligible i. e 0.

And, for rotational equilibrium of a body the total torque or the net torque acting on the body should be negligible or 0.

We can also say that when a body neither experiences any linear acceleration nor any angular acceleration the body is said to be in equilibrium.